Heretofore, fibers of nylon, polyester, or aramid are used as rubber reinforcing fibers that reinforce rubber products such as tires, belts, and hoses.
These rubber reinforcing fibers are usually subjected to immersion treatment by using an adhesive composition containing a copolymer latex for adhesives (generally, a butadiene-vinylpyridine copolymer latex, or a mixture of a butadiene-vinylpyridine copolymer latex and other rubber latex) and a resorcin-formalin resin to ensure their adhesiveness to rubber products. At this time, when the adhesive composition foams, the treatment operability of the fibers may be reduced.
As such an adhesive composition capable of reducing foaming during immersion treatment, for example, an adhesive composition containing a copolymer latex obtained by using a specific oligomer as a polymerization emulsifier and a resorcin-formalin resin has been proposed (ref: for example, the following Patent Document 1).